Female age and laying order drive variation of egg quality in blue tits

January 7, 2019, Max Planck Society

Little more than 50 years after the German ornithologist Wolfgang Makatsch published his book titled No Egg Is Like Another (Kein Ei gleicht dem anderen), new research at the Max Planck Institute for Ornithology in collaboration with the Max Planck Institute of Biochemistry and the University of Hohenheim reveals exactly how right he was. The study describes for the first time the egg albumen and yolk proteomes—that is, all measurable proteins—of a common songbird, the blue tit. It shows that breeding females can fine tune their eggs' composition to the needs of their young.

The quality of an egg resides in its size and its composition. In all egg-laying species, larger eggs produce larger, more viable and more performant offspring, while specific egg components (such as antioxidants or antimicrobial proteins) can support offspring growth, development or immunity. Egg quality varies broadly in wild animals and can even vary within a clutch and induce differences among siblings. To understand what drives this variation, researchers have turned to a population of blue tits (Cyanistes caeruleus) breeding in southern Germany. They measured the nutrient content of the eggs, as well as the individual concentrations of six carotenoids (adding three new compounds to the list of avian egg carotenoids) and almost 300 egg proteins, and explored how the complex composition of the eggs varies in the population.

Blue tits are small, socially monogamous songbirds that breed once per year. Females use the nutrients they acquire from their daily food to produce one egg per day until the clutch has seven to 15 eggs, and a total weight that often exceeds her own body mass. Such a reproductive endeavour is difficult to sustain, and larger clutches contain smaller eggs. Moreover, the capacity to acquire, synthesize and deposit egg nutrients varies among females, resulting in eggs with very different composition.

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Female penguins are getting stranded along the South American coast

January 7, 2019, Cell Press

Every year, thousands of Magellanic penguins are stranded along the South American coast—from northern Argentina to southern Brazil—1,000 kilometers away from their breeding ground in northern Patagonia. Now researchers reporting in Current Biology on January 7 have new evidence to explain the observation that the stranded birds are most often female: female penguins venture farther north than males do, where they are apparently more likely to run into trouble.

"Anthropogenic threats have been considered to threaten wintering Magellanic penguins along the coasts of northern Argentina, Uruguay, and southern Brazil; these include water pollution caused by oil development and marine transport as well as fishery-associated hazards, such as bycatch and depletion of prey species," says Takashi Yamamoto of the Institute of Statistical Mathematics in Tokyo. "Our results suggest that the northward spatial expansion likely increases the probability to suffer these risks, and particularly so in females."

Researchers knew that penguins stranded along the South American coast were three times as likely to be females. The question was: why?

While data were lacking, there wasn't any evidence to suggest that males and females split up for the winter. Now, Yamamoto and his colleagues find that in fact they do. The researchers recorded the migratory and diving behavior of 14 Magellanic penguins (eight males and six females) during the non-breeding period in 2017 using LAT 2500 geolocators (Lotek Wireless, Inc.).

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Swift parrot polyamory a new threat to critically endangered species' survival

Shortage of female swift parrots caused by sugar gliders wreaking ‘havoc’ on mating

Calla Wahlquist

Tue 4 Dec 2018 17.00 GMTLast modified on Wed 5 Dec 2018 14.16 GMT

Tasmania’s critically endangered swift parrots are facing a new threat to survival – polyamory.

A study by researchers at the Australian National University, published in the Journal of Animal Ecology, has found that a chronic shortage of female swift parrots caused by intensive predation by sugar gliders has wreaked havoc on the bird’s usually monogamous breeding habits and lowered the survival rate for young hatchlings.

Lead researcher Prof Rob Heinsohn said the unusual behaviour was caused by a significant disparity in the number of males and females in the parrots’ breeding grounds of the blue gum forests in south-east Tasmania. Surplus bachelor males were pressuring paired-up females for sex and getting into fights with paired males.

Heinsohn said that predation by sugar gliders, which were introduced to Tasmania from mainland Australia in the 1800s, had changed the gender ratio in the swift parrot population from a roughly equal number of male and female birds to three males to every female.

Females are at more risk from sugar gliders because the marsupials attack their tree-hollow nests while the females are incubating their eggs.

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After a bad winter in the ocean, female Magellanic penguins suffer most, study shows

Date:  November 7, 2018

Source:  University of Washington

Every autumn in the Southern Hemisphere, Magellanic penguins leave their coastal nesting sites in South America. For adults, their summer task -- breeding, or at least trying to -- is complete. Newly fledged chicks and adults gradually head out to sea to spend the winter feeding. They won't return to land until spring.

Yet life for these birds when they winter offshore is largely a mystery to the scientists who study Magellanic penguins -- and who advocate for their conservation amid declining population numbers.

"The winter period is something of a black box for us in terms of understanding Magellanic penguins," said Ginger Rebstock, a University of Washington research scientist. "We know the least amount about this part of their year."

But research by Rebstock and P. Dee Boersma, a UW professor of biology and founder of the Center for Ecosystem Sentinels, is starting to pry open that black box and discover how Magellanic penguins from one nesting site, Punta Tombo in Argentina, fare during the winter months. In a paper published Aug. 9 in the journal Marine Ecology Progress Series, they report that the Río de la Plata -- which drains South America's second-largest river system after the Amazon -- strongly influences oceanographic conditions in the Magellanic penguins' winter feeding waters. Those oceanographic features, they report, show up in the body conditions of Magellanic penguin females, but not males, when the penguins return to their nesting grounds in spring.

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Scientists remind their peers: Female birds sing, too

Date:  March 14, 2018

Source:  American Ornithological Society Publications Office

When North American ornithologists hear a bird singing, they're likely to assume it's a male. But in many species, the females sing too -- and a new commentary in The Auk: Ornithological Advancesargues that a better understanding of these unappreciated female songs could lead to advances in many aspects of bird biology.

Authors Karan Odom of Cornell University and Lauryn Benedict of the University of Northern Colorado both discovered the world of female birdsong through their own research. "I started studying California towhees 17 years ago, and I was fascinated by the duet vocalization given by females and males," says Benedict. "That led me to start looking for female song in other North American bird species, and I was surprised to learn that it was much more common than I expected. The reports of female song are buried in odd corners of the literature, but when you put them all together, you start to see some interesting patterns."

Though singing females were likely the norm among the ancestors of today's songbirds, female song today is understudied and is underrepresented in collections of bird sound recordings. This, say Odom and Benedict, may be result of bias toward the world's temperate regions -- though more widespread in temperate species than many ornithologists appreciate, female song is most common among tropical birds. They argue that better documentation of which species female song is present in and more detailed descriptions of female song structure and output could improve our understanding of birds' comparative physiology, neurobiology, behavioral ecology, evolution, and even conservation. Birds of conservation concern are often located and identified by song during surveys, and assumptions that all singing birds are male could mislead wildlife managers about the state of populations.

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Female birds call the shots in divorce

Date: July 20, 2016

Source: Monash University

Research is shedding new light on the causes of divorce in monogamous year-round territorial birds. A Monash University study of the endangered Purple-crowned Fairy-wren has discovered the females are calling the shots when it comes to breaking up.

Published in the journal Behavioral Ecology, the School of Biological Sciences' research studied 317 breeding pairs to learn what was driving the behaviour. As many as one in five avian pairs ended in divorce over nine years, and lead researcher Associate Professor Anne Peters said they were surprised to find it was the females who were more likely to break up.

"Females exhibit long term planning and are more likely to end their relationship when the opportunity for a better territory arises.

"We found females were prepared to wait, sometimes up to three years, for a good vacant spot to come up -- where the female owner has died or moved on."

Found in Western Australia's Kimberley region, it's estimated less than 10,000 Purple-crowned Fairy-wrens remain in the area. Unlike birds that move away from their territory and separate after breeding, the Fairy-wrens live together in pairs, year-round, in the same patch.

"These females are sitting there, they're not happy with their partner or their territory; they have an affair on the side and they're more likely to divorce. With divorce they get a different partner and a different territory. The territory seems to be more important than the partner," Associate Professor Peters said.

PhD candidate and first author Nataly Hidalgo Aranzamendi said the females were prepared to take drastic action to gain a better territory. "We found that older females sometimes kicked younger females out of their territories to claim these as their own."

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Do female birds mate with multiple males to protect their young?

Date: May 30, 2016

Source: KILDEN - information and news about gender research in Norway

Blue tit females mate with more than one male. Several possible blue tit fathers may then work together to stop predators from attacking their young, according to new research from the University of Bergen. Philosopher Claus Halberg believes this research challenges established ideas about the passive female.

"In many species, such as the blue tit, females often mate with multiple males. We've known this since the 1990s. The question has been why. For a long time it was thought it was to ensure that the offspring got the 'best' genes. But our studies indicate that it may have to do with completely different reasons," says Adele Mennerat.

Mennerat is a post-doctoral research fellow in the Department of Biology at the University of Bergen. She also teaches at the Centre for Women's and Gender Research.

Blue tits pair off in the winter. While only females build nests, they share the feeding task with the males when the young are born. But if the chicks are given a DNA test, it will often show that they have up to three or four different fathers. For the sake of simplicity, let's call these chicks that are not the offspring of the male feeding them, "extra-pair chicks."

"The main hypothesis has been that the fathers of the 'extra-pair chicks' had especially good genes and that this was why the female had mated with them. But around the year 2000, evolutionary biologists began to doubt whether this was the main explanation. Many researchers tried to show this was the case -- that is, there was a difference in genetic quality between the extra fathers and the feeding father -- but they found little evidence for this," explains Mennerat.

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Female birds can’t shake their colorful fathers, and other lessons from studying 6,000 species

Date: November 4, 2015

Source: McMaster University

The evolution of male songbirds as the colorful consorts of drab female partners is more complicated than long thought, says a McMaster researcher on a team that looked at nearly 6,000 species for a massive study published in the journal Nature.

Conventional wisdom has held that in many species, male birds were more colorful because they were competing for female attention, and that female birds were less colorful because they needed camouflage while guarding their nests.

Now advances in computing power and new methods that compare coloration in different species have allowed the researchers on the study to look at every species of passerine, the perching songbirds that make up about 60 per cent of the world's 10,000 species of birds.

The study offers impressive new evidence that supports some old theories while setting others to rest, explains Cody Dey, an author of the Nature paper who was completing his PhD in Biology at McMaster at the time of the research.

The question of plumage colour is significant, Dey, explains, because birds, especially males, give up so much to look so good, creating an evolutionary mystery that asks exactly what they gain in return for rendering themselves more vulnerable to predation. "These are the questions that have been asked since the start of ecology," he says.

Among the ideas the research supports is that females would have evolved to be even more different than males than they already are, except that every female inherits the genetic material of a colorful male -- an ancestry that is impossible to shake. "If colorful males do better, they're going to produce colorful daughters as well, even though it's not necessarily advantageous for the daughters," Dey says.

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Female birds get drabber when their males fool around

Kai Kupferschmidt 

4 November 2015 1:00 pm

Bird species in which one male can mate with many females tend to have more colorful males. But the promiscuity has an even stronger effect on females, making them drabber. That’s one of the more surprising conclusions in a new study of more than half of all living species of birds, which also reveals that a bird’s size and breeding location has a strong influence on the extravagance of its plumage.

“This paper is one of the most ambitious comparative studies ever conducted,“ says Geoffrey Hill, an ornithologist at Auburn University in Alabama, who was not involved with the work. But Richard Prum, an ornithologist at Yale University, says the paper is flawed because the team relied on pictures of birds in a book rather than observing them in the wild. “You couldn't study animal pheromones with scratch-and-sniff recreations."

Most scientists believe that bright colors signal good health or a great immune system. But why are some bird species more colorful than others? That’s been tough to resolve because it is hard to quantify how colorful a plumage is, says Bart Kempenaers, an ornithologist at the Max Planck Institute for Ornithology in Seewiesen, Germany. “How do you compare bright red with bright blue or yellow? That is the problem we had to solve."

Kempenaers and his colleagues tried a new approach: scanning pictures. The scientists focused on passerine birds, a group that makes up more than half of all known bird species and that is sometimes known as perching birds for their arrangement of toes—three pointing forward, one back. The researchers scanned illustrations in the Handbook of the Birds of the World, the only book covering every known living bird species, and then used a computer program to quantify how colorful each bird’s plumage is.

The tricky part was getting just one number that they could compare across species. For each bird, the scientists looked at six different patches of feathers (nape, crown, forehead, throat, upper breast, lower breast) and then identified the 1% of birds that were closest in color in the same patch. The more males, the higher the score for that patch. The researchers then calculated the average of the six patch scores for each bird. In essence, the scientists measured how "malelike" a bird appeared. But because male birds, in general, tend to be more colorful, that measure also works as a measure of how colorful a bird’s plumage is.

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Female cowbirds pay attention to cowbird nestling survival, study finds

Date: September 9, 2015

Source: University of Illinois at Urbana-Champaign

Summary: Brown-headed cowbirds have a reputation for being deadbeat parents: They lay their eggs in other birds' nests and then disappear, the story goes, leaving the care and feeding of their offspring to an unwitting foster family. A new study suggests, however, that cowbird moms pay close attention to how well their offspring do, returning to lay their eggs in the most successful host nests, and avoiding those that have failed.

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DNA that only females have

Date:

June 4, 2015

Source:

Uppsala Universitet

Summary:

In many animal species, the chromosomes differ between the sexes. The male has a Y chromosome. In some animals, however, for example birds, it is the other way round. In birds, the females have their own sex chromosome, the W chromosome. For the first, researchers have mapped the genetic structure and evolution of the W chromosome.

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Being lower in pecking order improves female tit birds' memory

Date:

December 9, 2014

Source:

Springer Science+Business Media

Summary:

When it comes to remembering where a tasty titbit was left, female great tit birds are miles ahead of their male counterparts. This ability might have evolved because the females come second when there’s food to be shared.

Great tits (Parus major) are highly intelligent and quick learners. These common European songbirds have interesting and ever-changing ways in which they find food, and even use tools such as conifer needles during foraging. Unlike most other members of the tit family, great tits are not food hoarders. Brodin and Urhan have previously demonstrated that they are able to observe where their hoarding relatives have made a stash, only to retrieve it up to 24 hours later.

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Female color perception affects evolution of male plumage in birds

Date:

November 25, 2014

Source:

University of Chicago Medical Center

Summary:

The expression of a gene involved in female birds' color vision is linked to the evolution of colorful plumage in males, reports a new study. The findings confirm the essential role of female color perception in mate selection and sexual dimorphism.

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Mom's hormones could make female magpie chicks more adventurous

Date:

September 1, 2014

Source:

University of Lincoln

Summary:

Female magpies have been shown to be more adventurous than their male siblings, according to new research. “The fact that observable differences between the first hatched and last hatched magpie’s behaviors exist indicates that mothers may be able to produce variable traits, possibly through adjustable transmission of maternal hormones or creating the conditions for sibling rivalry. Mothers could potentially produce a variety of personalities perhaps as an adaptive strategy in unpredictable environmental conditions," researchers say.

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Birdsong is not all about sexual selection: Female birds sing much more often than previously thought

Date:

March 5, 2014

Source:

Leiden, Universiteit

Summary:

In 71 percent of all songbird species with available data, the female sings, too. This is remarkable because in the wake of Darwin’s theory of evolution, birdsong has generally been seen as a characteristic of male birds, allowing them to compete with other males and attract females. The exciting question now is how females apparently repeatedly lost their song in the course of evolution. Why did they stop singing in some lineages, but not in others?

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